Electrophotography refers to producing photographic images by electrical means, and xerography is a form of electrophotography for copying documents and other graphic matter. Xerographic copiers are extensively used in a variety of environments, such as offices, libraries, and educational institutions.
The basic elements of a xerographic copier are well known to those skilled in the art. A light source forms an electrostatic latent image of an original document on a photosensitive medium. The photosensitive medium, as it moves within the copier, travels adjacent a source of tiny plastic particles called toner. The electrostatic force of the latent image on the photosensitive medium attracts the toner, thereby providing a developed image of toner particles on the surface of the photosensitive medium.
In color xerographic copiers, to form a complete color image the photosensitive medium must form a separate image for each color of toner used (usually primary colors) and transfer these separate images, one at a time, to a second medium, where the different colors are superimposed one upon the other. This second medium is called a transfer medium. After the complete color image is formed on the transfer medium, the complete color image is transferred through electrostatic charges to an image receptor (normally a sheet of paper or plastic). The image receptor is then passed through a heating device which melts the toner and fixes the image onto the image receptor.
After the complete color image has been transferred from the transfer medium, some toner particles remain clinging to the surface of the transfer medium. A cleaning station, mounted adjacent the transfer medium, removes the clinging toner from the transfer medium to prevent the clinging toner from contaminating subsequent images. The cleaning element of the cleaning station is normally spring loaded so that the cleaning element is forced to contact the transfer medium; however, the cleaning element cannot remain in constant contact with the surface of the transfer medium, or else the separate color images would be removed from the transfer medium before the next color image could be superimposed. Therefore, it is necessary that the cleaning element contact the transfer medium after the complete color image has been transferred to the image receptor, and then pull away from the transfer medium before encountering the first color component of the subsequent image. A device such as a solenoid-operated shaft pulls the cleaning element away from the transfer medium at the proper times.
As is well known in the prior art, the cleaning station gradually becomes filled with toner and that toner must be removed. The cleaning station must be removed from the xerographic copier before the toner can be removed therefrom. In conventional xerographic copiers, access to the cleaning station is difficult. As a result, it is difficult to remove the cleaning station without spilling toner into the copier as the cleaning station is removed. The toner is a fine powder and tends to become airborne when spilled, and this airborne toner settles throughout the copier, contaminating images formed on the photosensitive medium and causing abrasive damage to various moving parts.
When removing the cleaning station, care must be taken not to scrape the cleaning element across the transfer medium to avoid damage to the transfer medium. This is a problem because as the cleaning station is pulled from the copier, the cleaning element is pulled from the solenoid-operated shaft and springs forward against the transfer medium.
An additional problem occurs when the cleaning station is returned to the copier after cleaning the blade. The cleaning element must be aligned with the solenoidoperated shaft for the cleaning station to fit properly. To align the cleaning element, that element must be manually pressed against the springs while the cleaning station is inserted in the copier. This makes the insertion of the cleaning station in the copier awkward, and can lead to damage of the transfer medium if the cleaning element were released prematurely and sprung forward.
As is also well known in the prior art, the cleaning element of the cleaning station gradually degrades and must be replaced. In conventional xerographic copiers, the cleaning station must be removed to replace the cleaning element. Therefore, the same problems discussed above are encountered when replacing the cleaning element.
More recently, laser printers have become popular office machines. As is known to those skilled in the art, laser printers are usually constructed with print engines similar to those used in xerographic copiers. A rasterscanned laser beam creates the latent image directly on the photosensitive medium in a laser printer. After the image is created on the photosensitive medium, the printing process is similar to that in a xerographic copier. Even more recently, color laser printers and xerographic printers utilizing other techniques for creating a latent image on the photosensitive medium have become popular. Many of these xerographic printers also have cleaning stations presenting the problems discussed above.
Therefore, there is a need in color electrophotographic print engines or color laser print engines for a simpler apparatus and process for removing and replacing cleaning stations and related cleaning elements without damaging other internal parts.